超声波辅助提取低褐变程度香蕉皮中总酚的研究

本试验首先比较了微波真空干燥、真空冷冻干燥以及热风干燥对香蕉皮干燥后褐变程度的影响。其次,以微波真空干燥得到的香蕉皮为原料,采用正交试验对香蕉皮总酚的提取工艺进行研究,确定了超声波辅助提取香蕉皮中总酚的最佳工艺条件。结果表明:微波真空干燥和真空冷冻干燥的香蕉皮褐变程度远低于热风干燥。香蕉皮中总酚的最佳提取工艺条件为:料液比1:20(g/mL)、60%的乙醇溶液、70℃条件下超声波(固定功率120 W)作用40 min,总多酚提取率最高,香蕉皮总酚的提取量达36.95 mg/g(干基)。     

香蕉皮热烫防褐变工艺条件的研究

采用L9(34)正交实验研究了热烫处理中热烫温度、热烫时间、热烫固液比以及柠檬酸添加量对香蕉皮浆液褐变度和皮中多酚氧化酶(PPO)活性的影响。正交实验结果表明,香蕉皮热烫处理的优化条件为:热烫温度为100℃、热烫时间为5min、热烫固液比为1∶6、加酸量为0.6%。在此条件下对香蕉皮进行热烫处理验证实验,测得香蕉皮浆液褐变度为0.117,香蕉皮中PPO酶活为16U,对香蕉皮的加工过程中控制褐变有明显效果。     

石榴果皮酶促褐变底物的研究

研究了石榴在贮藏期间果皮褐变度(BD)与总酚和单宁的变化关系,探讨了多酚氧化酶(PPO)活性变化趋势,利用薄层层析和HPLC鉴定了引起石榴果皮酶促褐变的底物。结果表明:石榴果皮单宁含量较高,贮期单宁含量下降迅速,且单宁含量下降速率与果皮褐变度呈正相关,分析得出引起石榴果皮酶促褐变的底物主要是单宁。     

香蕉皮单宁的提取及其提取物的抑菌抗氧化活性

以香蕉皮为原料,采用微波提取法,以单宁提取率为评价指标,在单因素试验基础上,通过响应面法优化了香蕉皮单宁提取工艺;滤纸片法测定了单宁对细菌、霉菌和酵母菌的抑菌性能;通过对O-2·和·OH的清除能力,确定了香蕉皮单宁的抗氧化能力。结果表明:香蕉皮单宁微波提取的最优工艺条件为,乙醇体积分数75%、提取时间为80 s、微波功率375 W、料液比1∶30(g∶m L),在此条件下单宁的提取率为87.04%;抑菌试验结果显示,香蕉皮单宁对大肠杆菌、金黄色葡萄球菌、根霉、青霉及酵母菌都有一定的抑菌效果,对大肠杆菌的最低抑菌浓度为0.78 mg/m L,金黄色葡萄球菌和酵母菌为6.25 mg/m L,霉菌为1.56 mg/m L;香蕉皮单宁对超氧阴离子自由基和羟自由基具有较好的清除能力,并在低浓度时(<1.0 mg/m L)抗氧化性要高于Vc,在浓度为1.8mg/m L时,香蕉皮单宁对超氧阴离子和羟自由基的清除率可达(66.04±3.926)%和(73.14±4.128)%。     

竹笋加工关键技术研究

试验对建瓯丰富的竹笋的关键加工技术进行了研究。结果表明,在竹笋采收后,立即在切割部位涂上复合被膜剂（0.015%蔗糖酯+0.015%海藻酸钠+0.015%植酸+0.02%柠檬酸）进行抗褐变处理,可以有效的延缓竹笋褐变,并在切片时进行二道抗褐变处理可有效地抑制竹笋的褐变,延长竹笋的保鲜期;将抗褐变处理后的竹笋采用复合酶解工艺（时间30min、温度50℃、0.02%单宁酶+0.02%木瓜蛋白酶）,使单宁含量降解至0.08mg.g^-1,脲氨酸含量为0.009mg.g^-1,基本去除了单宁苦物质,并抑制了脲氨酸络合物的产生;将酶解后的竹笋采用真空预冷和单体速冻相结合的工艺,使解冻后竹笋脱水液中未检测出酪氨酸、半胱氨酸溶出量,有效抑制了白色沉淀物在货架期间的生成。     

超声波细胞破碎法提取香蕉皮中水解单宁的工艺研究

以香蕉皮粉末为原料,用超声波细胞破碎法提取水解单宁。选取有机溶剂种类、料液比、体积分数、提取时间和超声功率作为影响因子,以水解单宁的提取率作为响应值,进行单因素实验,在此基础上进行Box-Behnken设计和响应面分析。结果表明,香蕉皮中水解单宁的最佳提取工艺条件为料液比1∶30(g/mL)、丙酮体积分数50%、提取时间15min、超声功率120 W,提取率的预测值为78.03%,实际值为78.11%,说明响应面分析能够很好地对香蕉皮中水解单宁的提取工艺进行优化。     

百香果浑浊果汁在储藏过程中发生非酶褐变原因的研究

把百香果浑浊果汁作为研究对象,以褐变度BI值为检测指标,跟踪其在储藏过程中引起非酶褐变的HMF(5-羟甲基糠醛)、VC、花色苷、缩合单宁、多酚等化学组分。采用通径分析的统计分析方法,解析了百香果浑浊果汁在储藏过程中非酶褐变的主要原因。结果表明,在25℃和5℃避光储藏条件下,百香果浑浊果汁中HMF,VC、花色苷、缩合单宁、多酚等成分的变化与百香果浑浊果汁褐变度BI值的变化密切相关;在25℃避光储藏条件下百香果浑浊果汁的非酶褐变主要由花色苷引起,花色苷与缩合单宁的交互作用是引起非酶褐变的第一决定因素;在5℃避光储藏条件下百香果浑浊果汁的非酶褐变主要由缩合单宁引起,花色苷与HMF的交互作用是引起非酶褐变的第一决定因素。     

香蕉皮单宁提取物对大肠杆菌的抑菌机理探究

研究香蕉皮单宁对大肠杆菌的抑菌机理,为香蕉皮的高效利用以及新型食品生物抑菌剂的开发提供理论基础。采用二倍稀释涂布平板法测定香蕉皮单宁对大肠杆菌的最低抑菌浓度(MIC)。通过测定菌液中碱性磷酸酶(AKP)、核酸和葡萄糖等含量变化,反映菌体细胞壁完整性、细胞膜完整性、消耗糖量变化,以此为指标对抑菌机理做出初步分析。香蕉皮单宁对大肠杆菌的最低抑菌浓度(MIC)为2.5mg/m L。菌液中碱性磷酸酶(AKP)前后含量无明显变化;菌液中核酸存在明显差异,1MIC实验组是对照的两倍。香蕉皮单宁通过破坏细胞膜的完整性发挥抑菌作用。     

板栗栗仁褐变及其控制方法研究

板栗的栗仁加工过程中褐变发生与栗仁的单宁含量有一定的相关性,板栗各部位的单宁含量不同,缝合线处高于表面高于栗仁心部,单宁含量越高,褐变越容易发生。加工过程中的水质、温度、时间、ｐＨ值可以防止褐变的发生。过氧化物酶能够促进褐变的发生,用热汤的方法可以杀死酶的活性,抑制褐变的发生。热烫栗仁４ｍｉｎ可以将酶全部杀死,不再发生由过氧化酶而引起的褐变现象。不同的护色液可以减轻或防止褐变的发生,在试验用的６种     

葡萄贮藏过程中的褐变初探

葡萄贮藏过程中,单宁、有机酸和维生素Ｃ含量均呈下降趋势,ＳＯ２处理可抑制这些变化。随着贮期延长,浆果内部出现褐变。浆果褐变与浆果中有机酸的含量的绝对值没有直接联系,与有机酸代谢变化的梯度大小有关;与褐变时浆果中单宁的含量呈显著负相关（ｒ＝－０．９４３８）。由于有机酸、维生素Ｃ的减少,有机酸、维生素Ｃ对多酚氧化酶的抑制作用减少,使其活性增加,导致单宁等多酚类物质氧化,从而产生褐变。ＳＯ２处理可以减少并延缓褐变。     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.     

Analysis for organic residues from aids to polymerization used to make plastics intended for food contact

Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography-mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (¹     

Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants

Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.     

Focus on China's Paper Industry

In the English section of this issue, 〈China Paper Newsletters〉 will introduce ＂National Development and Reform Commission Issued Announcement for Selection of Major Preliminary Research Projects for the ＇13th Five-Year Plan＇＂, ＂2013 Annual Report of China＇s Paper Industry＂, and news of projects and other policies.     

Listen to downstream & search for innovation

正Nowadays,textile enterprises are all taking efforts in transformation and upgrading,like improving producing capacity and optimizing production structure to face market downturn.It claimed a higher request to the standard of textile equipments.In the upcoming of ITMA ASIA+CITME 2014exhibition,this magazine have interviewed several branch associations and a series of relative enterprises,to summarize industrial developing status